Regioisomeric Giant Triblock Molecules: Role of the Linker

Abstract

In this study, polyhedral oligomeric silsesquioxane (POSS) based giant triblock molecules with precisely defined regio‐configuration are modularly prepared through highly efficient coupling reactions. The length of the linker connecting neighboring nanoparticles is elaborately designed to regulate the geometric constraints. The triblock molecules adopt a folded packing during phase separation, and the regio‐configuration imparts direct influence on the self‐assembly behaviors. The ortho‐isomers form periodic structures with a larger domain size, larger interfacial curvature, and enhanced phase stability. The regio‐effect is closely related to the length and symmetry of the linker. As the linker extends, the neighboring particles gradually decouple, and the regio‐effect diminishes. The symmetry of the linker shows an even more profound impact. This work quantitatively scrutinized the role of the linker, opening an avenue for engineering the assembled structures with molecular precision.

Influence of Regio-Configuration and Molecular Geometry on the Assembly Behavior of Giant Molecules

“…Due to the architectural constraint, however, the C 4 POSS/VPOSS moieties must overcome large steric hindrances to migrate together to alleviate excess unfavorable interfacial contact. 32,33 The stability of the phase structure in the para-and metaisomers is thus apparently lower than that in the ortho-isomer. The differences between these regio-isomers clearly highlight the importance of molecular geometry.…”

“…A library of triblock giant molecules with precisely defined sequences and regio-configurations were modularly prepared using different types of POSS units (Scheme 1). Vinyl POSS with two hydroxyl groups on the para-, meta-, or ortho-position (VPOSS−(OH) 2 ) was first prepared following our earlier studies (Scheme 1a), 32,33 were constructed by successively connecting these POSS units through Steglich esterification, while the regio-configuration could be regulated using a specific regio-isomeric POSS unit in the middle (Scheme 1d).…”

“…A library of triblock giant molecules with precisely defined sequences and regio-configurations were modularly prepared using different types of POSS units (Scheme ). Vinyl POSS with two hydroxyl groups on the para -, meta -, or ortho -position (VPOSS–(OH) 2 ) was first prepared following our earlier studies (Scheme a), , and the six residual vinyl groups were then replaced with different ligands through the thiol–ene click reaction, affording n -butyl-functionalized POSS (C 4 POSS–(OH) 2 ), n -dodecyl-functionalized POSS (C 12 POSS–(OH) 2 ), and fluorinated POSS (FPOSS–(OH) 2 ) (Scheme b). On the other hand, monocarboxylic acid-functionalized POSS units were prepared by converting the hydroxyl group of VPOSS–OH into the carboxylic group, followed by installing different surface functionalities (VPOSS–COOH, C 4 POSS–COOH, C 12 POSS–COOH, and FPOSS–COOH; Scheme c).…”

“…For this set of samples ( p -, m -, and o -VFC 4 ), the miscibility between the two end blocks (C 4 POSS and VPOSS) favors the formation of C 4 POSS/VPOSS contacts, despite the lack of covalent connection. Due to the architectural constraint, however, the C 4 POSS/VPOSS moieties must overcome large steric hindrances to migrate together to alleviate excess unfavorable interfacial contact. , The stability of the phase structure in the para - and meta -isomers is thus apparently lower than that in the ortho -isomer. The differences between these regio-isomers clearly highlight the importance of molecular geometry.…”